An electromagnetic hand writing input device (or a hand writing tablet) is typically used by a user with a tablet and an electromagnetic pen type stylus (after, saying electromagnetic pen). The conventional electromagnetic pen is a pen having a “sharp-shaped” pen-tip inserted in it's front part for writing or selecting objects on the tablet. An erasing device, which is a slim cylindrical type electromagnetic eraser, is deposed on tail part (or rear end part) of the electromagnetic pen for erasing words, patterns, or marks on the tablet.
When a user painting on the tablet with the “sharp-shaped” pen-tip, most technique of painting can be performed by this “sharp-shaped” pen-tip, but it can not exactly simulate the unique paint effects of oil paintings which are painting by palette knifes. It is because the palette knifes for oil painting have different shapes and different sizes. The shapes of the palette knifes include various kinds of shapes, for example sharp shape, needle shape, elliptic shape, and so forth. Therefore, the paint effects of oil paintings are unique and varied. Furthermore, people can use the same palette knife with actions of pressing, dragging, wiping and scraping to paint an oil painting having different paint effect therein, or people can use a palette knife to scrap the oil painting for removing the unsatisfied drawing or color and then painting it again. These are the effects and functions that the current “sharp-shaped” electromagnetic pens applied to tablets can not achieve and have.
Besides, many conventional electromagnetic pens have a erasing device deposed on their tail parts, and there are many patents about these electromagnetic pens have a erasing device deposed on their tail parts, for example U.S. Pat. Nos. 4,697,050, 5,325,110, 5,401,916, 5,576,502, and 5,793,360. However, most of the electromagnetic pens disclosed by these patents have some drawbacks. Taking patent U.S. Pat. No. 4,697,050 as an example, the patent U.S. Pat. No. 4,697,050 discloses a electromagnetic pen 10 having a lead 12 deposed on one end of the electromagnetic pen 10 and an eraser 14 deposed on another end of the electromagnetic pen 10 (as FIG. 1). A user controls the oscillator circuit 18 to emit the electromagnetic signal with special frequency by pressing the switch 16 or the switch 17 and the tablet recognizes that the electromagnetic pen 10 is in writing mode or in erasing mode by the electromagnetic signal emitted by the oscillator circuit 18. However, the electromagnetic pen 10 has a drawback that it has a need of the spring structure 19 for moving the eraser 14 back. Therefore, the structure of the electromagnetic pen 10 is more complicated and the cost and difficulty for fabricating the electromagnetic pen 10 is increased. The another drawback of the electromagnetic pen 10 is that the eraser 14 needs to contact the tablet and rub against the tablet continuously during erasing because the eraser 14 need to be moved back to turn on the switch 15 by touching the tablet for turning on the erasing mode. Therefore, the eraser 14 made of plastics or rubbers will be worn out frequently and it has a need of changing the eraser 14 frequently. Therefore, the cost for using the electromagnetic pen 10 is increased and it is inconvenient to the user.
The patent U.S. Pat. No. 5,576,502 discloses an electromagnetic pen 20 having a cylindrical shape (as FIG. 2). There is a coil 22 deposed in the tail part (or rear end part) of the electromagnetic pen 20 for erasing. The coil 22 is covered by a back cover 24 having circular head and there is a coil spring 26 deposed under the back cover 24 for moving the back cover 24 back to stop erasing when the electromagnetic pen 20 is moved away from the tablet. When erasing by the electromagnetic pen 20, the back cover 24 touch the tablet and back cover 24 is pressed by the tablet. Therefore, the back cover 24 moves toward the coil spring 26 for compressing the coil spring 26 to turn on the switch in the electromagnetic pen 20 for turning on the erasing mode. Therefore, the electromagnetic pen 20 needs to contact the tablet continuously during erasing. However, the stricture of this “pressing-type” electromagnetic pen 20 is more complicated and the cost for fabricating this “pressing-type” electromagnetic pen 20 is increased because of the need of the coil spring 26. Besides, the uncomfortable noises are caused by rubbing between the electromagnetic pen 20 and tablet during erasing, and it is easy to damage the surface of the tablet and to wear the tail part of the electromagnetic pen 20.
The patent U.S. Pat. No. 5,793,360 discloses an electromagnetic pen 20 having a digitizer eraser method wherein an electromagnetic pen is used to select the different cursors having different shapes for writing or erasing. In this method, an application program is applied to recognize the current cursor for judging whether the user erases words or objects on the tablet. However, the electromagnetic pen adopted by this patent is the same with the electromagnetic pens disclosed in the patent U.S. Pat. No. 4,697,050 and the patent U.S. Pat. No. 5,576,502. All of them are the “pressing-type” electromagnetic pen 20 and they have the same drawbacks.
As above mentioned patents, most of the tail parts of the electromagnetic pens only have single function, and there is no any tail part of above-mentioned electromagnetic pens having multi-functions. Therefore, the electromagnetic pens only have single function and single operation mode, and they can not achieve the demand of diversification and multi-function for electric devices. Furthermore, most erasers (or erasing devices) deposed on the tail parts of the electromagnetic pens have a circular head as the back cover 24 illustrated in FIG. 2. Therefore, like the “sharp-shaped” pen-tip of the electromagnetic pen, they can not be applied to paint a drawing having characteristics and paint effects of oil paintings on the tablet by actions of pressing, dragging, wiping and scraping.
Therefore, in view of foregoing drawbacks of the conventional electromagnetic pens, there is a need to provide a multi-function electromagnetic pen having characteristics of simple structure and low cost, and particularly to provide a electromagnetic pens which has no need of a spring structure deposed on the tail part of the electromagnetic pen and has functions of erasing, magnifying, palette knife, and so forth. Furthermore, the tail part of multi-function electromagnetic pen has no need to contact (or touch) and rub the tablet during erasing, and the noises and damages caused by the contact and the rub between the tail part of multi-function electromagnetic pen and the tablet can be prevented.